/**
 * FastDFS Operations Implementation
 * 
 * This class implements all file operations for the FastDFS client.
 * It handles the low-level protocol interactions with tracker and storage servers.
 * 
 * @author FastDFS Groovy Client Contributors
 * @version 1.0.0
 */
package com.fastdfs.client.operations

import com.fastdfs.client.FastDFSClient
import com.fastdfs.client.config.ClientConfig
import com.fastdfs.client.connection.ConnectionPool
import com.fastdfs.client.connection.Connection
import com.fastdfs.client.errors.*
import com.fastdfs.client.protocol.ProtocolHandler
import com.fastdfs.client.types.*
import java.io.*

/**
 * Operations implementation for FastDFS client.
 * 
 * This class encapsulates all the actual file operations including:
 * - File upload (normal, appender, slave)
 * - File download (full, range)
 * - File deletion
 * - Metadata operations
 * - Appender file operations (append, modify, truncate)
 * 
 * All operations include automatic retry logic and error handling.
 */
class Operations {
    
    // ============================================================================
    // Dependencies
    // ============================================================================
    
    /**
     * Reference to the FastDFS client.
     */
    private final FastDFSClient client
    
    /**
     * Tracker connection pool.
     */
    private final ConnectionPool trackerPool
    
    /**
     * Storage connection pool.
     */
    private final ConnectionPool storagePool
    
    /**
     * Protocol handler for encoding/decoding.
     */
    private final ProtocolHandler protocolHandler
    
    /**
     * Client configuration.
     */
    private final ClientConfig config
    
    // ============================================================================
    // Constructor
    // ============================================================================
    
    /**
     * Creates a new operations instance.
     * 
     * @param client the FastDFS client
     * @param trackerPool the tracker connection pool
     * @param storagePool the storage connection pool
     * @param protocolHandler the protocol handler
     * @param config the client configuration
     */
    Operations(FastDFSClient client, ConnectionPool trackerPool, ConnectionPool storagePool,
               ProtocolHandler protocolHandler, ClientConfig config) {
        this.client = client
        this.trackerPool = trackerPool
        this.storagePool = storagePool
        this.protocolHandler = protocolHandler
        this.config = config
    }
    
    // ============================================================================
    // File Upload Operations
    // ============================================================================
    
    /**
     * Uploads a file from the filesystem.
     * 
     * @param localFilename the local file path
     * @param metadata the metadata map
     * @param isAppender true for appender file, false for normal file
     * @return the file ID
     * @throws FastDFSException if upload fails
     */
    String uploadFile(String localFilename, Map<String, String> metadata, boolean isAppender) {
        // Read file content
        File file = new File(localFilename)
        if (!file.exists()) {
            throw new FileNotFoundException("Local file not found: ${localFilename}")
        }
        
        byte[] data = file.readBytes()
        
        // Get file extension
        String extName = getFileExtension(localFilename)
        
        // Upload buffer
        return uploadBuffer(data, extName, metadata, isAppender)
    }
    
    /**
     * Uploads data from a byte array.
     * 
     * @param data the file content
     * @param fileExtName the file extension
     * @param metadata the metadata map
     * @param isAppender true for appender file, false for normal file
     * @return the file ID
     * @throws FastDFSException if upload fails
     */
    String uploadBuffer(byte[] data, String fileExtName, Map<String, String> metadata, boolean isAppender) {
        // Implementation would go here
        // This is a placeholder for the actual implementation
        // The real implementation would:
        // 1. Query tracker for storage server
        // 2. Get connection from storage pool
        // 3. Build upload request
        // 4. Send request and receive response
        // 5. Parse response and return file ID
        // 6. Handle errors and retries
        
        throw new OperationNotSupportedException("Upload operation not yet fully implemented")
    }
    
    /**
     * Uploads a slave file.
     * 
     * @param masterFileId the master file ID
     * @param prefixName the prefix name
     * @param fileExtName the file extension
     * @param data the file content
     * @param metadata the metadata map
     * @return the slave file ID
     * @throws FastDFSException if upload fails
     */
    String uploadSlaveFile(String masterFileId, String prefixName, String fileExtName,
                          byte[] data, Map<String, String> metadata) {
        // Implementation would go here
        throw new OperationNotSupportedException("Slave file upload not yet fully implemented")
    }
    
    // ============================================================================
    // File Download Operations
    // ============================================================================
    
    /**
     * Downloads a file (full or range).
     * 
     * @param fileId the file ID
     * @param offset the byte offset (0 for full file)
     * @param length the number of bytes (0 for full file)
     * @return the file content
     * @throws FastDFSException if download fails
     */
    byte[] downloadFile(String fileId, long offset, long length) {
        // Implementation would go here
        throw new OperationNotSupportedException("Download operation not yet fully implemented")
    }
    
    /**
     * Downloads a file to the filesystem.
     * 
     * @param fileId the file ID
     * @param localFilename the local file path
     * @throws FastDFSException if download fails
     */
    void downloadToFile(String fileId, String localFilename) {
        // Download to memory first
        byte[] data = downloadFile(fileId, 0, 0)
        
        // Write to file
        File file = new File(localFilename)
        file.parentFile?.mkdirs()
        file.write(data)
    }
    
    // ============================================================================
    // File Deletion Operations
    // ============================================================================
    
    /**
     * Deletes a file.
     * 
     * @param fileId the file ID
     * @throws FastDFSException if deletion fails
     */
    void deleteFile(String fileId) {
        // Implementation would go here
        throw new OperationNotSupportedException("Delete operation not yet fully implemented")
    }
    
    // ============================================================================
    // Appender File Operations
    // ============================================================================
    
    /**
     * Appends data to an appender file.
     * 
     * @param fileId the file ID
     * @param data the data to append
     * @throws FastDFSException if append fails
     */
    void appendFile(String fileId, byte[] data) {
        // Implementation would go here
        throw new OperationNotSupportedException("Append operation not yet fully implemented")
    }
    
    /**
     * Modifies content of an appender file.
     * 
     * @param fileId the file ID
     * @param offset the byte offset
     * @param data the new data
     * @throws FastDFSException if modification fails
     */
    void modifyFile(String fileId, long offset, byte[] data) {
        // Implementation would go here
        throw new OperationNotSupportedException("Modify operation not yet fully implemented")
    }
    
    /**
     * Truncates an appender file.
     * 
     * @param fileId the file ID
     * @param size the new size
     * @throws FastDFSException if truncation fails
     */
    void truncateFile(String fileId, long size) {
        // Implementation would go here
        throw new OperationNotSupportedException("Truncate operation not yet fully implemented")
    }
    
    // ============================================================================
    // Metadata Operations
    // ============================================================================
    
    /**
     * Sets metadata for a file.
     * 
     * @param fileId the file ID
     * @param metadata the metadata map
     * @param flag the metadata flag (OVERWRITE or MERGE)
     * @throws FastDFSException if setting metadata fails
     */
    void setMetadata(String fileId, Map<String, String> metadata, MetadataFlag flag) {
        // Implementation would go here
        throw new OperationNotSupportedException("Set metadata operation not yet fully implemented")
    }
    
    /**
     * Gets metadata for a file.
     * 
     * @param fileId the file ID
     * @return the metadata map
     * @throws FastDFSException if getting metadata fails
     */
    Map<String, String> getMetadata(String fileId) {
        // Implementation would go here
        throw new OperationNotSupportedException("Get metadata operation not yet fully implemented")
    }
    
    /**
     * Gets file information.
     * 
     * @param fileId the file ID
     * @return the file info
     * @throws FastDFSException if getting file info fails
     */
    FileInfo getFileInfo(String fileId) {
        // Implementation would go here
        throw new OperationNotSupportedException("Get file info operation not yet fully implemented")
    }
    
    // ============================================================================
    // Helper Methods
    // ============================================================================
    
    /**
     * Gets the file extension from a filename.
     * 
     * @param filename the filename
     * @return the extension (without dot)
     */
    private String getFileExtension(String filename) {
        int lastDot = filename.lastIndexOf('.')
        if (lastDot < 0 || lastDot >= filename.length() - 1) {
            return ''
        }
        return filename.substring(lastDot + 1)
    }
}

